1. Field of the Invention
The invention relates to pigging of pipelines, and in particular to launching of pigs into a pipeline from a subsea launch location.
2. Background Art
Pigging is a process of running an object called a pig through the inside of a pipeline from one point to another. The pigs are pushed along by the flow of fluid inside the pipeline. Pigs are often elastomeric spheres or cylinders used to clean or scrape the inside of a pipeline. Pigs can be complex devices with their own on-board power and systems that perform inspections or do mechanical tasks.
Pigs are usually installed in a pipeline through a device called a pig launcher. When installed at a subsea location, there must not be any significant loss of fluid from the pipeline into the environment. Typically a subsea pig launcher may launch one to three pigs. The pig launcher is then recovered to the surface, refilled with pigs, and reinstalled subsea. This process is costly and time consuming.
In accordance with one aspect of the invention, there is provided a pig launcher adapted for subsea installation to a subsea pipeline manifold for launching pigs into a subsea pipeline. The pig launcher includes a dual-bore collet connector and a magazine for storing pigs. The dual-bore collet connector is adapted for subsea engagement with a mating connector on the subsea pipeline manifold, and has a first bore for passing the pigs into the subsea manifold and at least a second bore for receiving pipeline fluid from the subsea pipeline manifold. The magazine can index at least one pig to at least one launch position. The magazine is coupled to the dual-bore collet connector for ejecting a pig at the launch position into and through the first bore of the dual-bore collet connector in a stream of the pipeline fluid received through the second bore of the dual-bore collet connector.
In accordance with another aspect, the invention provides a pig launcher adapted for subsea installation to a subsea pipeline manifold for launching multiple pigs into a subsea pipeline. The pig launcher includes a dual-bore collet connector adapted for subsea engagement with a mating connector on the subsea pipeline manifold, and a rotary magazine for storing multiple pigs. The dual-bore collet connector has a first bore for passing the pigs into the subsea manifold, and at least a second bore for receiving pipeline fluid from the subsea pipeline manifold. The rotary magazine includes a rotor defining pig storage locations and having an actuator coupled to the rotor for rotating the rotor to index the pigs to at least one launch position. The rotary magazine is coupled to the dual-bore collet connector for ejecting a pig at the launch position into and through the first bore of the dual-bore collet connector in a stream of the pipeline fluid received through the second bore of the dual-bore collet connector.
In accordance with yet another aspect, the invention provides a subsea pig launching system for launching pigs into a subsea pipeline. The subsea pig launching system includes a launcher manifold and a pig launcher. The launcher manifold is adapted for coupling between an upstream section of the subsea pipeline and a downstream section of the subsea pipeline to convey pipeline fluid from the upstream section of the pipeline through the launcher mainfold and to the downstream section of the subsea pipeline. The pig launcher has a dual-bore collet connector and a magazine for storing a multiplicity of pigs. The collet connector is engageable with a mating connector on the launcher manifold. The dual-bore collet connector has a first bore for passing the pigs into the launcher manifold and at least a second bore for receiving pipeline fluid from the launcher manifold. The magazine indexes at least one pig to at least one launch position, and is coupled to the dual-bore collet connector for ejecting a pig at the launch position into and through the first bore of the dual-bore collet connector in a stream of the pipeline fluid received through the second bore of the dual-bore collet connector. The launcher manifold has a closure valve for closing off flow of pipeline fluid to the first bore of the collet connector when the collet connector is released, and the launcher manifold has at least one valve for diverting pipeline fluid from the upstream section of the subsea pipeline to the second bore of the collet connector for ejecting the pig at the launch position.